Methods and systems disclosed herein relate generally to correcting numerical models and more specifically to using sea surface height (SSH) data to correct ocean forecast models.
Systems exist that enable velocity observations of ocean currents from sources such as drifters at the surface or under water, and/or current meters either moored or on ships, to correct an ocean forecast model by using historical observations saved in a database to relate the observed velocity to temperature and salinity structure throughout the water column. These systems relate velocity measurements to salinity and temperature using historical observations, and enable the use of a plethora of existing, worldwide sources, for example, but not limited to, drifters and current meters, of current measurements for ocean model correction. These systems make use of existing historical data to develop region specific velocity/salinity-temperature correlations, and are computationally efficient and compatible with existing super-computer ocean forecasting systems operated daily to enable operational use.
SSH is a measure of the difference between the actual SSH at any given time and place, and that which it would have if the ocean were at rest. Satellite altimeters measure the round-trip travel time of a radar pulse to estimate SSH. Ocean forecast model corrections have historically been done using salinity and temperature profiles and satellite SSH. Another method for using SSH to correct ocean models uses data assimilation through the construction of synthetic ocean profiles. This method can be inefficient, can introduce representativeness errors, and can potentially damp out information from profile observations. Yet another method uses data assimilation through model-derived error covariances according to Eq. (1).
                              〈                                    (                              x                -                                  〈                  x                  〉                                            )                        ⁢                                          (                                  x                  -                                      〈                    x                    〉                                                  )                            T                                〉                =                  [                                                                                          U                    T                                    ⁢                                      B                    T                                    ⁢                                      U                    T                    T                                                                              0                                                                    0                                                                                  U                    S                                    ⁢                                      B                    S                                    ⁢                                      U                    S                    T                                                                                ]                                    (        1        )            where xT=[T1 . . . TN, S1 . . . Sn], T=Temperature, S=Salinityn=number of vertical levels< >≡average operatorUT or S=vector of standard deviations for T or SBT or S=correlation matrix for T or SThis method can lead to undesirable model self-confirmation effects. Ocean data assimilation systems require a method to correlate observations at two vertical locations in the ocean.
What is needed is a system that enables SSH measurements from sources such as satellites to correct an ocean forecast model by using historical observations saved in a database to relate the observed SSH to temperature and salinity structure throughout the water column. The needed system could enable the use of a plethora of existing, worldwide sources of SSH for ocean model correction. The needed system could make use of existing historical data to develop region-specific SSH/salinity-temperature correlations. What is further needed is a computationally efficient method that is compatible with existing super-computer ocean forecasting systems operated daily to enable operational use. What is still further needed is a system that allows the direct assimilation of SSH data from satellites to improve efficiency and reduce representativeness errors. What is even still further needed is historical observation data to provide the relations between T, S, and geopotential (ø) to prevent errors due to model drift in ensemble methods.